The present invention relates to methods and apparatus for automatically inspecting machine-made tobacco products, such as cigarettes, cigars or cigarillos, to insure that the content of each subsequently formed package meets production standards. More particularly, the present invention relates to an improved method and apparatus for detecting, for example, that a cigarette is missing from a group or that a cigarette in the group is improperly filled prior to packaging the group.
It is well known to inspect a tobacco product, such as a cigarette, prior to packaging for the purpose of detecting an inadequate or loose charge of tobacco shreds near the end. On the one hand, such an inspection is necessary because an insufficiently or loosely filled cigarette cannot be properly handled by cigarette packaging machinery. Furthermore, such an inspection is desirable from the standpoint that a smoker is annoyed and risks injury if a cigarette is improperly filled. That is, tobacco shreds are likely to fall from the end of the cigarette as the smoker removes the cigarette from the package creating a mess. Furthermore, if the smoker ignites an improperly filled cigarette, a large flame can result which could startle or burn the smoker.
An inspection is also necessary from the standpoint that a subsequently formed package must contain a predetermined number of cigarettes. If a cigarette is missing, the purchaser is cheated.
It is, therefore, desirable to reject cigarettes which cannot be properly handled so as to maintain high speed production. It is also desirable to avoid customer complaints by detecting missing and improperly filled cigarettes so that a defective package is not subsequently formed.
One known technique for detecting missing and improperly filled cigarettes is mechanical inspection. Mechanical inspection employs pins which are pushed against the end portions of cigarettes. The extent to which a pin penetrates indicates the amount of tobacco shreds in the end portion of a cigarette. However, mechanical inspecting is undesirable due to the risk of damage to cigarettes during inspection due to compressing the end portions. Furthermore, decreased production results since the mechanical response time is relatively long which means that inspecting cannot be performed at a speed compatible with the speed of modern cigarette making and packaging machinery.
Another known technique is electrostatic inspection as disclosed in U.S. Pat. Nos. 3,951,267 and 3,993,194. The speed of electrostatic inspection is relatively high. However, the amount of moisture in the tobacco, changes in humidity, temperature and other ambient conditions and the high amount of electrical noise in the vicinity of machinery for making and packaging cigarettes affect the accuracy with which missing and improperly filled cigarettes are detected.
Also known are optical techniques for detecting missing and improperly filled cigarettes. U.S. Pat. No. 3,812,349 discloses an optical inspecting apparatus which includes a laser, an optics system, a photodetector and a comparison circuit to check light reflected from the tobacco in the end portion of a cigarette. However, the disclosed apparatus only checks one cigarette at a time because each cigarette is also inspected for surface flaws. Therefore, the device operates at a slow production speed. Furthermore, the apparatus is expensive due to the cost of the laser.
U.S. Pat. No. 3,473,037 discloses an optical inspecting apparatus which includes a single light source, an optics system and an array of photocells to check light reflected from the tobacco in the end portions of cigarettes in a preformed group. However, the optics system is relatively complicated and expensive. This patent also discloses a photo-imaging system including a vidicon which involves complexity and high cost. Furthermore, U.S. Pat. No. 3,980,567 discloses a fiberoptics inspecting apparatus for illuminating and sensing light reflected from the tobacco in the end portions of cigarettes. However, the disclosed apparatus is relatively expensive due to the cost of the fiber-optics.
One objective of the present invention is to provide a high speed method and apparatus for detecting cigarettes missing from a preformed group and improperly filled cigarettes in the group prior to packaging.
Another objective is to provide a method and apparatus for detecting missing and improperly filled cigarettes with a high degree of accuracy so that normal groups are packaged and only defective groups are rejected.
An additional objective is to minimize the effects of varying ambient conditions on the accuracy with which missing and improperly filled cigarettes are detected.
It is a further objective to provide an improved optical method and apparatus for detecting missing and improperly filled cigarettes which is characterized by high speed and accuracy and at the same time has a relatively low initial cost and is reliable and economical in operation.